﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;
using System.Xml;
using System.Xml.Serialization;
using System.IO;

namespace Celeriq.Utilities
{
    /// <summary />
    public static class Extensions
    {
        internal static Expression<T> Compose<T>(this Expression<T> first, Expression<T> second, Func<Expression, Expression, Expression> merge)
        {
            // build parameter map (from parameters of second to parameters of first)
            var map = first.Parameters.Select((f, i) => new {f, s = second.Parameters[i]}).ToDictionary(p => p.s, p => p.f);

            // replace parameters in the second lambda expression with parameters from the first
            var secondBody = ParameterRebinder.ReplaceParameters(map, second.Body);

            // apply composition of lambda expression bodies to parameters from the first expression 
            return Expression.Lambda<T>(merge(first.Body, secondBody), first.Parameters);
        }

        /// <summary>
        /// Concatenate Lambdas using the AND operation
        /// </summary>
        public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
        {
            return first.Compose(second, Expression.And);
        }

        /// <summary>
        /// Concatenate Lambdas using the OR operation
        /// </summary>
        public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
        {
            return first.Compose(second, Expression.Or);
        }

        /// <summary>
        /// Can compare 2 strings with case insensitivity
        /// </summary>
        public static bool Contains(this string source, string toCheck, StringComparison comp)
        {
            return source.IndexOf(toCheck, comp) >= 0;
        }

    }
}